Dynamics of lane formation in driven binary complex plasmas

The dynamical onset of lane formation is studied in experiments with binary complex plasmas under microgravity conditions. Small microparticles are driven and penetrate into a cloud of big particles, revealing a strong tendency towards lane formation. The observed time-resolved lane formation process is in good agreement with computer simulations of a binary Yukawa model with Langevin dynamics. The laning is quantified in terms of the anisotropic scaling index, leading to a universal order parameter for driven systems.Comment: 4 pages, 3 figures, movies available at http://www.mpe.mpg.de/pke/lane-formation

Residual gas entering high density hydrogen plasma: rarefaction due to rapid heating

The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy

Residual gas entering high density hydrogen plasma: rarefaction due to rapid heating

The interaction of background molecular hydrogen with magnetized (0.4&nbsp;T) high density (1–5&nbsp;×&nbsp;10 20 &nbsp;m −3 ) low temperature (∼3&nbsp;eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center, vibrational temperatures reached 1&nbsp;eV. Rotational temperatures obtained from the Q( v&nbsp;=&nbsp;1) branch were systematically ∼0.1&nbsp;eV lower than the Q( v&nbsp;=&nbsp;0) branch temperatures, which were in the range of 0.4–0.8&nbsp;eV, typically 60% of the translational temperature (determined from the width of the same spectral lines). The latter is attributed to preferential excitation of translational degrees of freedom in collisions with ions on the timescale of their in-plasma residence time. Doppler shifts revealed co-rotation of the molecules with the plasma at an angular velocity an order of magnitude lower, confirming that the Fulcher emission connects to background molecules. A simple model estimated a factor of 90 rarefaction of the molecular density at the center of the plasma column compared to the residual gas density. Temperature and density information was combined to conclude that ion-conversion molecular assisted recombination dominates plasma recombination at a rate of 1&nbsp;×&nbsp;10 −15&nbsp;m 3&nbsp;s −1 . The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy.</p

New linear plasma devices in the trilateral euregio cluster for an integrated approach to plasma surface interactions in fusion reactors

New linear plasma devices are currently being constructed or planned in the Trilateral Euregio Cluster (TEC) to meet the challenges with respect to plasma surface interactions in DEMO and ITER: i) MAGNUM-PSI (FOM), a high particle and power flux device with super-conducting magnetic field coils which will reach ITER-like divertor conditions at high magnetic field, ii) the newly proposed linear plasma device JULE-PSI (FZJ), which will allow to expose toxic and neutron activated target samples to ITER-like fluences and ion energies including in vacuo analysis of neutron activated samples, and iii) the plasmatron VISION I. a compact plasma device which will be operated inside the tritium lab at SCK-CEN Mol, capable to investigate tritium plasmas and moderately activated wall materials. This contribution shows the capabilities of the new devices and their forerunner experiments (Pilot-PSI at FOM and PSI-2 Julich at FZJ) in view of the main objectives of the new TEC program on plasma surface interactions. (C) 2011 Forschungszentrum Julich, Institut fur Energieforschung-Plasmaphysik. Published by Elsevier B.V. All rights reserved

Simulation of the Neutral Inventory in the Pilot-PSI Beam

The Eunomia code is used to study the neutral species in and near a hydrogen plasma beam. Eunomia is a non-linear Monte Carlo transport code that solves the neutral equilibrium, given a fixed background plasma. The code is developed to study the neutral inventory of Pilot-PSI and Magnum-PSI, linear devices developed to study plasma surface interactions in similar conditions as expected in the ITER divertor. Results show the influence of elastic collisions and the outer vessel wall on the neutral species. In the center of the 2 cm diameter Pilot-PSI beam the results show a strong coupling to the plasma. Only millimeters away from the center, the neutral flow, temperature and density are strongly influenced by recombination processes at the vessel wall ((c) 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim